Devices that separate gases, liquids and solids work on a variety of principles. In oil extraction applications gravity separators are widely used for the purpose of separating oil from water or vice versa, and also for separating gas from emulsions containing extracted water and oil. Such gravity separators have been used both on land-based crude oil and gas process plants as well as on offshore production platforms, in spite of their significant associated installation costs due to their large space and weight requirements.
Most separation systems handle well streams from several wells. The wells are choked to a common pressure into a manifold and the streams of oil, water, gas and solids extracted from the wells are conducted via a common pipe or line to the separator. To reduce the momentum of the incoming gas/liquid well stream in the separator, inlet devices have normally been mounted inside the separator. Traditionally, the inlet devices have been simple splash plates or sets of vanes, even though, more recently, new inlet cyclones have been introduced to make benefit from high g-forces to eliminate foaming in the separator. However, such inlet cyclones may create a very difficult emulsion of oil and water that often can be impossible to separate in the gravity separator. They also add to the weight, space requirement and complexity of the separator.
Recently, some oil companies experience new challenges for their separation process. The fact that some of the wells are oil continues and some are water continues may cause complex emulsion patterns. Water droplets can trap oil droplets that, in their turn, may trap small water droplets. The various wells must be choked differently, and as a result thereof there will be large variations in droplet sizes. This adds to the complexity of the incoming gas-oil-water mixture. The water cut for each well will change during the production, typically from 0% water to 90% water. Accordingly the inlet separation system needs to be flexible in handling the various types of mixtures. However, there are difficulties in obtaining inlet separation systems that are flexible and that do not add a considerable weight and volume to the separator arrangement.